(1) Field of the Invention
The present invention relates to a method for switching a digital signal in an optical fiber from an input fiber to a plurality of output fibers and an apparatus for performing such switching. More specifically, the present invention relates to a method for switching a digital signal in an optical fiber from an input fiber to a plurality of output fibers by means of at least one laser-activated amplifier and a plurality of optical attenuators without requiring a conversion from an optical signal into an electrical signal and at high switching speeds.
(2) Description of the Prior Art
There exist numerous methodologies whereby optical signals may be switched from one fiber to another without first converting to an electronic signal and then back to an optical signal. Most of these methods involve some change in the medium to bend the light beam and achieve a physical switching of the input beam into two or more output beams. Some of the methods used include micro-electro-mechanical systems (MEMS), liquid crystals, tiny ink-jet bubbles, thermo-optical switches, tunable lasers, or using sound waves. As a result of requiring a change in the propagating medium to achieve switching, most of these switching methods have relatively slow switching speeds, e.g., on the order of 100 Hz. There are methods for switching light with light without changing the medium. These methods typically rely on nonlinearities. The problem with a nonlinear system is that it does not work well for switching broadband signals, which can be viewed as sums of narrowband signals. The sum of many narrowband signals will have a different response than the response of a single narrowband signal.
What is needed is a methodology for switching an optical input signal into a plurality of optical outputs that does not depend upon nonlinearities or upon the implementation of a change in medium giving rise to unacceptably slow switching speeds.